Field of the Invention
The present invention relates to an image sensor unit, an image reading apparatus, and an image forming apparatus.
Description of the Related Art
Image sensor units used for a scanner, a copying machine and a multifunction machine have been known. Patent Document 1 discloses an image sensor unit that includes a light guide where a light emitter and a bent portion are formed, and a circuit board on which a light source and an image sensor are mounted. In the image sensor unit in Patent Document 1, light emitted from a light source is incident on an incident surface of a bent portion of a light guide, passes through the insides of the bent portion and the light emitter, and is linearly emitted from a light emission surface of the light emitter toward an object of illumination. Light reflected by the object of illumination is received by an image sensor, whereby an image of the object of illumination is read. Thus, by using the light guide where the light emitter and the bent portion are formed, a surface-mounted LED package can be used as the light source, and the cost of the image sensor unit can be reduced.
Patent Document 1
Japanese Laid-open Patent Publication No. 2013-31152
However, in the image sensor unit as described above, the light source and the image sensor are mounted on the same circuit board. Consequently, a part of the light emitted from the light source does not enter the light guide but becomes stray light and can be received by the image sensor.